Tripodal Carboxylate Bridge Enables Buried Interface Passivation Toward High-Performance and Durable Perovskite Solar Cells

The abundant trap states at the buried interface of perovskite solar cells (PSCs) significantly deteriorate device performance and stability. While monodentate or bidentate carboxylates can passivate undercoordinated metal sites, their linear geometry hinders dual-sided passivation. Herein, we introduce non-planar nitrilotriacetic acid trisodium (NTANa) as a bifacial passivator at the SnO₂/perovskite buried interface. Compared to monodentate and bidentate analogues of sodium acetate and sodium oxalate, tripodal NTANa with 3D spatially distributed carboxylate tooth can simultaneously passivate undercoordinated Sn⁴⁺ and Pb²⁺ trap states on both sides of the interface via strong coordinative interactions. The tridentate NTANa interlayer also enhances electronic coupling and optimizes energy level alignment to facilitate electron transport at the buried interface. Consequently, the target NTANa-modified PSCs deliver a markedly increased power conversion efficiency (PCE) of 25.32% with a high fill factor of 0.84. By suppressing interfacial charge accumulation and ion migration, the unencapsulated device demonstrates significantly enhanced operational stability with a T₉₀ of 836 h at maximum power point tracking (MPPT) under continuous one-sun illumination. This work demonstrates the effectiveness of multidentate molecular design for dual-sided interfacial passivation toward efficient and durable PSCs.